The present invention relates to a platform for a processing chamber and, more particularly, to a platform for supporting semiconductor substrates during thermal processing and chemical deposition of thin film applications, for example, during film deposition, oxide growth, etching, and thermal annealing.
When heating a substrate, it is desirable to heat the substrate rapidly and in a uniform manner so that all the regions of the substrate are heated to the same temperature. Rapid heating of the substrate reduces processing time and, therefore, increases the processing rate for a given substrate. Ultimately, with increased processing rates the cost of processing a semiconductor substrate is reduced. Furthermore, when processing semiconductor substrates it is desirable to limit impingement of the processing gases, which form the thin film depositions on the substrate, on to a single sidexe2x80x94the device sidexe2x80x94of the substrate.
Conventional platforms typically support the semiconductor substrate by the peripheral portion of the semiconductor substrate. In this manner, both the top and bottom surfaces of the substrate are exposed, which permits rapid heating of the substrate. However, with these configurations, the non-device side of this semiconductor substrate is not isolated from the process gases, which may result in undesirable depositions being formed on the nondevice side of the substrate.
In U.S. Pat. No. 5,487,127, to Gronnet et al., the semiconductor substrate is supported at its peripheral edge by an annular support and is heated by plurality of light pipes which are positioned on one side of the substrate and treated by process gases by a shower-head-like gas injection system which is positioned on the other side of the substrate. However, with the increase in the size of wafers, this sort of arrangement may result in warpage of the semiconductor substrate since it is supported only at its peripheral edge.
In U.S. Pat. No. 4,834,022, to Mahawili, a chemical vapor deposition reactor is disclosed which includes a heater platform which provides uniform support to the wafer. The platform includes a recessed circular well for holding the semiconductor wafer therein. While the size of the platform can be increased to accommodate larger substrates, as the dimensions of the platform increase, the thickness necessarily increases in order to provide sufficient structural capacity. However, as the thickness of the platform increases the heat transfer rate reduces. Hence, the rapid processing of the semiconductor substrates may be impaired because of the reduced heat transfer rates.
More recently, platforms for supporting a semiconductor substrate during rapid high temperature processing have been made from silicon carbide coated graphite. In some processes, the thermal shock characteristics of the silicon carbide coated graphite platforms can limit the platforms"" application. While other materials, such as quartz, generally exhibit greater thermal shock characteristics, quartz has other characteristics that limit its application. Since the substrate holder also acts as an isolating medium for light transmission, quartz has heretofore been found unsuitable in such application since quartz is transparent over most temperature ranges.
Consequently, there is a need for a platform which can support a semiconductor substrate during thermal processing in a manner to limit depositions of processing gases to a single sidexe2x80x94the device sidexe2x80x94of the substrate and permit rapid heating of the substrate. Furthermore, there is a need for a platform which has sufficient structural integrity to support large semiconductor substrates, on the order of up to 300 mm or greater, without impeding the heat transfer from the heater source to the substrate. Additionally, there is a need for a platform which can provide support for a semiconductor substrate during rapid high temperature processing while also limiting light transmission, thus isolating the reactor chamber from stray light, which could interfere with certain processes, for example emissivity measurements.
As will be understood, the platform of the present invention provides numerous advantages over prior known platforms. The platform provides a support for a semiconductor substrate during thermal processing in a manner that permits the non-device side of the substrate to be isolated from the processing chamber in a conventional processing reactor. At the same time, the platform permits the heat transfer from the heater assembly of the reactor to the substrate to be maximized and, yet, provides a platform which can support semiconductor substrates on the order of 300 mm in diameter or greater. The platform further isolates the substrate from light transmission from the heater assembly.
In one form, a platform for supporting a semiconductor substrate during processing in a processing chamber, which includes a heater and a rotatable housing, includes a body having a first support surface for supporting the substrate thereon and a second support surface for being supported by the rotatable housing over the heater in the processing chamber. The body comprises a quartz material, with at least a portion of the quartz material being adapted to be opaque to block transmission of photon energy through that portion during heating.
In preferred form, the quartz material includes a coating over at least a portion of the quartz material, with the coating adapting the quartz material to be opaque. For example, the coating may comprise a composite film of silicon and silicon carbide.
In other forms, the body comprises first and second member, with the first member including a first support surface and the second member including a second support surface and a third support surface. The third support surface supports the first member on the second member and the second support surface is provided for being supported by the rotatable housing.
In another form of the invention, a platform for supporting a semiconductor substrate during processing in a processing chamber, which includes a heater and a rotatable housing, includes first and second member. The first member includes a first support surface for supporting a substrate. The second member includes second and third support surfaces, with the first member being supported on the second support surface of the second member. The third support surface is for supporting the first and second members in the processing chamber over the heater by the rotatably housing. At least one of the first and second members comprises a quartz material, with at least a portion of the quartz material being adapted to be opaque to limit transmission of light from the heater to the processing chamber.
For example, the quartz material may include a coating over that portion, with the coating adapting the quartz material to be opaque. Preferably, the coating comprises a composite film of silicon and silicon carbide.
A method of making a platform for use in high temperature processing according to the present invention includes providing a quartz body, which is dimensioned for use as a substrate processing chamber platform, and forming a coating on at least a portion of the quartz material for adapting a quarts body to be opaque.
In one aspect, the coating is formed by depositing a film of silicon and silicon carbide. Preferably, the film is uniformly deposited. The quartz body is preferably heated to a temperature in a range of 700xc2x0 to 1100xc2x0 C. while depositing the silicon and silicon carbide onto the quartz body. More preferably, the quartz body is heated to a temperature in a range of approximately 900xc2x0 to 1000xc2x0 C. In other aspects, the film of silicon and silicon carbide is deposited onto the quartz body under pressure in a range of 50 to 400 Torr and more preferably in a range of 200 to 350 Torr. The coating is formed in a process which extends over a deposition time in a range of about 2 to 5 hours.
In other forms, the quartz body is placed in a chamber of a high temperature oven, and an organo-silane gas and hydrogen gas are injected into the chamber. The quartz body is heated to a temperature in a range of approximately 700xc2x0 to 1100xc2x0 C. and the chamber is pressurized to a pressure in a range of approximately 50 to 400 Torr.
These and other objects, advantages, purposes and features of the invention will be apparent to one skilled in the art from a study of the following description taken in conjunction with the drawings.